1. Field of the Invention
The present invention relates to a travel following system for a vehicle, which is designed to allow the subject vehicle to travel following a preceding vehicle in a relatively low speed range.
2. Detailed Description of the Related Art
A Stop & Go system having the following functions is known as a conventional travel following system operated in a lower speed range:    (1) when a preceding vehicle has been detected in a speed range from the stopped state to a predetermined vehicle speed, the subject vehicle is allowed to travel following the preceding vehicle;    (2) when the subject vehicle is stopped automatically following the stopping of the preceding vehicle during operation of the system, the stopped state of the subject vehicle is maintained;    (3) the driver is informed of the starting of the preceding vehicle;    (4) the starting of the operation of the system is carried out by a switching operation by the driver rather than automatically: and    (5) a condition for canceling the system is any of the cases where
the driver has carried out the braking operation,
the driver has carried out an accelerating operation,
sight of the preceding vehicle has been missed, and
another vehicle has intruded into between a vehicle provided with the system (which will be referred to as a subject vehicle) and a preceding vehicle.
One example of a Stop & Go system is known from Japanese Patent Application Laid-open No. 11-48826.
In the above-described conventional Stop & Go system, when a preceding vehicle is stopped, the subject vehicle is stopped automatically without a braking operation by a driver. For this reason, if the driver excessively relies on the system to be neglectful of the braking operation, there is a possibility that the braking operation by the driver is retarded when the automatic braking cannot cope with a case where another vehicle or a pedestrian dashes out from the side or a case where a preceding vehicle is suddenly stopped.
In the case where the system is operated from a state in which the subject vehicle has been once stopped, if the driver tries to start the subject vehicle automatically in response to the starting of a preceding vehicle, it matters whether or not the driver is ready to drive the vehicle. In the conventional system, in order to confirm a driver's will, the driver is informed of that a preceding vehicle has been started, and the system is operated when a switch is turned on by the driver, However, if the system is designed as described above, there is a possibility that a switching operation is troublesome and the convenience of the system is detracted. If the switching operation by the driver who has been informed of the starting of the preceding vehicle is retarded, the subject vehicle may be left behind the preceding vehicle, and cannot travel following the preceding vehicle in some cases, For this reason, the driver is forced to be tense so as not to retard the switching operation. Also in this case, the convenience is detracted.